Arguments are never for the benefit of the person you're arguing against as that person likely will not change their mind. I believe there are a few studies that strengthen that claim. So, when I argue with strangers, it's for the benefit of the lurkers who fall somewhere between both of our ideas and are looking for something to push them in a direction. They're willing to hear both sides or are simply entertained at the idea of someone they dislike being verbally flagulated. The people who are physically around me are more than likely not at a point in their lives where they're open to discussion to be convinced out of the positions they hold.

I can't imagine anything more futile than trying to reason with someone who hasn't arrived at their beliefs by using it. However online the best outcome is I convince someone I'm right. At worst, I'm entertainment.